Morphine, which is known as the major component of opium alkaloids, has been frequently used in drugs such as anesthetics and analgesics. However, it is disadvantageous in that it causes drug dependence and is liable to cause morphinomania.
It is known that naloxone represented by the following formula (II): ##STR3## shows a narcotic antagonist action, similar to the compound of the present invention. However, naloxone has only a slight analgesic action, which does not make it particularly suitable as an analgesic. Thus, there has been an urgent demand for a drug which has potent analgesic and narcotic antagonist actions and yet exhibits low drug dependence.